students = [["Anna", 90], ["Tom", 78], ["Jerry", 85], ["Lucy", 92]]
#1.统计学生人数
count = len(students)
print(count)
#2.增加两名学生
stu_1 = ["Mark", 87]
stu_2 = ["Eva", 80]
students.append(stu_1)
students.append(stu_2)
print(students)
#3.删除第二位学生
del students[1]
print(students)
